This applied research project will utilize systematic experimental methodology to collect information relevant to the design and operation of effective narcotics and polydrug abuse treatment programs. The major focus is upon illicit drug use -- supplemental drug use among methadone maintenance patients and relapse to illicit narcotics use among methadone detoxification and post-detoxification patients. Experiments seek to understand the determinants of such drug use and to develop effective treatment interventions for reducing supplemental drug use and narcotics relapse. Experiments address several areas of narcotic addiction and addiction treatment. With methadone maintenance patients we will conduct basic clinical pharmacology studies of pharmacological and suggestibility influences upon patients' response to methadone dose alterations, and we will examine pharmacological and environmental influences upon methadone patients' response to intravenous opiate supplements. In applied methadone maintenance studies we will explore the value of urinalysis-contingent positive reinforcement procedures as aids to reducing illicit supplemental drug use. Applied outpatient methadone detoxification studies will experimentally assess the influence of pharmacological and suggestibility factors upon detoxification success, and will evaluate the utility of urinalysis-contingent reinforcement as an aid to preventing narcotics relapse. Positive reinforcement procedures will be further evaluated as aids for increasing post-addicts' enrollment in and continued participation in outpatient treatment with the narcotic antagonist naltrexone. Overall, these investigations should contribute to improved understanding of the pharmacological and environmental circumstances which contribute to illicit drug use, and should reveal effective intervention techniques for reducing illicit drug abuse.